CN108273279B

CN108273279B - High-efficiency low-consumption hydrogen chloride separation method

Info

Publication number: CN108273279B
Application number: CN201711216529.7A
Authority: CN
Inventors: 朱好言; 张伟; 孙道成; 朱明华; 王长宽; 苗安伟; 杨海菲; 孙蕊蕊; 何凯
Original assignee: Liaocheng Luxi Chemical Engineering Co Ltd
Current assignee: Liaocheng Luxi Chemical Engineering Co Ltd
Priority date: 2017-11-28
Filing date: 2017-11-28
Publication date: 2021-04-02
Anticipated expiration: 2037-11-28
Also published as: CN108273279A

Abstract

The invention discloses a high-efficiency low-consumption hydrogen chloride separation method, which separates hydrogen chloride in mixed gas by a rectification method to obtain 99.9 percent of HCL gas for outward delivery; according to the condition that the boiling points of all components of the mixed gas are different and lower, a tower kettle reboiler introduces an ice machine to pressurize, then a gas phase R22 is used as a heat source of the tower kettle reboiler and an HCL heater to provide heat, and a cooled R22 is decompressed and then used as a refrigerant for a tower top secondary condenser; the tower bottom material is decompressed and then used as a refrigerant for a tower top first-level condenser, and the tower bottom material is heated and then sent to the next procedure. The whole process fully utilizes the cold and hot load of R22, no additional steam is needed, and the production cost is reduced.

Description

High-efficiency low-consumption hydrogen chloride separation method

Technical Field

The invention relates to an energy-saving optimization process for separating and purifying hydrogen chloride from mixed gas of hydrogen chloride, CH2F2 and a small amount of HF, CH2CLF, CL2, CH2CL2 and the like, which is suitable for the production process of R32(CH2F2) in fluorine chemical industry.

Background

In the production process of R32(CH2F2), the mixed gas at the outlet of the reflux column of the reactor contains hydrogen chloride (58 wt%), CH2F2 (40 wt%) and small amounts of HF, CH2CLF, CL2, CH2CL2 and the like, and the hydrogen chloride in the mixed gas is separated and then R32(CH2F2) is purified. The traditional process adopts a falling film absorption method to obtain 31 percent of waste hydrochloric acid. The mixed gas contains high content of hydrogen chloride, large amount of waste acid and a small amount of fluoride, so that the waste acid has high treatment difficulty and becomes a difficult problem for enterprises.

R22 (CHCIF 2) and R32(CH2F2) are used as common low-temperature refrigerants, and low-pressure gas phases R22 (CHCIF 2) and R32(CH2F2) are pressurized to about 1.4Mpa by a compressor, condensed to normal-temperature gas phases and conveyed to each user, and then decompressed to be used as low-temperature (-20 ℃ and-35 ℃) refrigerants. The low temperature heat load released by R22(CHCLF2), R32(CH2F2) condensation is not utilized effectively.

Disclosure of Invention

In order to overcome the defects, the invention provides a high-efficiency low-consumption hydrogen chloride separation method, which realizes zero steam consumption, recycles cold and heat energy of R22 (CHCIF 2) and R32(CH2F2) and reduces the production cost.

The following technical scheme is adopted to achieve the purpose:

separating HCL gas by rectification according to the different boiling points of HCL and R32(CH2F2) in the mixed gas. Directly feeding the mixed gas with the temperature of 10-27 ℃ and the pressure of 1.0-1.2 Mpa into a hydrogen chloride rectifying tower, controlling the pressure at the top of the tower to be 1.0-1.1 Mpa, the temperature to be 25-28 ℃ and the pressure at the bottom of the tower to be 1.0-1.13 Mpa, and the temperature to be 10-15 ℃;

the temperature of the tower bottom material is lower, and R22 gas with the ice machine outlet of 1.4Mpa of 35 ℃ is directly conveyed to a reboiler of the rectifying tower bottom to be used as a heat source for providing heat; the condensed R22 (CHCIF 2) liquid phase is decompressed to 0.15Mpa (-28 ℃) and enters a tower top secondary condenser as a refrigerant to condense the tower top gas phase.

The main component of the material extracted from the tower bottom is R32(CH2F2), the pressure is reduced to 0.2Mpa, and the material is conveyed to the first-stage condensation at the tower top and is used as a refrigerant for recovering cold;

heating the low-temperature hydrogen chloride gas at the tower top to 15-20 ℃, then delivering the hydrogen chloride gas, and heating the finished product hydrogen chloride by using the R22 gas at 1.4Mpa35 ℃ at the outlet of the ice maker; mixing the condensed R22 (CHCIF 2) liquid phase with the reboiler outlet R22 (CHCIF 2) at reduced pressure of 0.15Mpa (-28 ℃), and feeding into a tower top secondary condenser; the normal pressure R22 (CHCIF 2) gas is sent back to the ice machine to be recycled after being pressurized.

Preferably, the whole separation process does not generate fluorine-containing waste hydrochloric acid, and the problems of difficult treatment of the waste hydrochloric acid and environmental protection are solved.

Preferably, a high concentration of 99.9% hydrogen chloride gas is obtained and delivered to the relevant plant as a feedstock for the production of methyl chloride.

Preferably, the whole separation process has no steam consumption, and 858kg/h of steam can be saved;

preferably, the refrigerant of the condenser at the top of the separation process is condensate of an outlet R22 (CHCHLF 2) of an ice maker, and the amount of the condensate is about 9800kg/h per hour; in the scheme, the required refrigerant amount is unchanged, the gas at an outlet R22 (CHCIF 2) of the ice maker is directly conveyed to a reboiler at the tower kettle, and the tower kettle material is heated by heat energy; after decompression, the gas phase at the top of the tower is condensed by using the cold energy of the gas phase, so that the energy utilization rate is improved, and an outlet condenser of an ice machine is saved;

preferably, the materials extracted from the tower bottom are washed by water after being decompressed, the temperature is-35 ℃ after decompression, and the recovered cold energy is used for gas phase condensation at the tower top.

Preferably, the hydrogen chloride gas extracted from the tower top is heated to normal temperature from-27 ℃, then is conveyed to a related device for use, and is condensed and decompressed by utilizing the R22(CHClF2) gas at the outlet of an ice maker as a heat source and then is conveyed to a condenser at the tower top as a refrigerant.

Preferably, the hydrogen chloride separation process follows a cold and hot energy balance, increasing the electricity consumption of the ice crusher pressurizing R22 compared with the traditional process.

Compared with the prior art, the invention has the beneficial effects that:

waste hydrochloric acid is not generated in the hydrogen chloride separation process, so that the environmental protection problem is solved;

the low-temperature heat load of the gas phase R22(CHCl 2) is recovered to replace steam, 858kg of steam is saved per hour, and the production cost of R32(CH2F2) is reduced;

r22 (CHCHLF 2) and R32(CH2F2) cold and heat are recycled, the energy utilization rate is improved, and the system separation process with similar properties can be optimized and modified by referring to the method.

Drawings

FIG. 1 is a schematic flow chart.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

The invention is further described below with reference to the drawings and examples to facilitate understanding by those skilled in the art:

example 1:

a high-efficiency low-consumption hydrogen chloride separation method comprises the steps of enabling mixed gas to enter an HCL rectifying tower, enabling gas at the top of the tower to enter a first-stage condenser, enabling part of the gas to enter a second-stage condenser after the first-stage condenser, enabling gas-liquid mixture to enter a reflux tank, enabling liquid to reflux, heating gas extracted by an HCL heater, and delivering the gas obtained by heating the gas to obtain 99.9% hydrogen chloride.

The material in the tower bottom enters a reboiler of the tower bottom, the gas-liquid mixture returns to the HCL rectifying tower after the gas is heated by normal temperature R22 (CHCHLF 2) gas from an ice machine, the material extracted from the tower bottom is decompressed and then enters a first-stage condenser to be used as a refrigerant, and the heated material enters a water washing process.

And respectively feeding the normal-temperature gas phase R22(CHCl 2) from the ice maker into an HCL heater and a tower kettle reboiler, reducing the temperature, mixing under reduced pressure, feeding into a tower top secondary condenser to serve as a refrigerant, heating to form a normal-temperature gas phase R22(CHCl 2) at the temperature of-35 ℃, and returning to the ice maker to pressurize for recycling.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A high-efficiency and low-consumption hydrogen chloride separation method is characterized in that: according to HCL and R32-CH in the mixed gas₂F₂Separating HCL gas by a rectification method when the boiling points are different; directly feeding the mixed gas with the temperature of 10-27 ℃ and the pressure of 1.0-1.2 Mpa into a hydrogen chloride rectifying tower, controlling the pressure at the top of the tower to be 1.0-1.1 Mpa, the temperature to be 25-28 ℃ and the pressure at the bottom of the tower to be 1.0-1.13 Mpa, and the temperature to be 10-15 ℃;

the temperature of the tower bottom material is lower, and R22 gas with the ice machine outlet of 1.4Mpa of 35 ℃ is directly conveyed to a reboiler of the rectifying tower bottom to be used as a heat source for providing heat; condensed R22-CHCHLF₂The liquid phase is decompressed to 0.15 Mpa-28 ℃ and enters a secondary condenser at the top of the tower to be used as a refrigerant to condense the gas phase at the top of the tower;

the main component of the material extracted from the tower bottom is R32-CH₂F₂Reducing pressure to 0.2Mpa, and delivering to the tower top for primary condensation as coldRecovering cold energy from the medium;

heating the low-temperature hydrogen chloride gas at the tower top to 15-20 ℃, then delivering the hydrogen chloride gas, and heating the finished product hydrogen chloride by using the R22 gas at 1.4Mpa35 ℃ at the outlet of the ice maker; condensed R22-CHCHLF₂Liquid phase and reboiler outlet R22-CHCHLF₂Decompressing to 0.15 Mpa-28 ℃ and entering a second-stage condenser at the top of the tower after mixing; normal pressure R22-CHCHLF₂The gas is sent back to the ice maker to be pressurized and recycled.